Update swagger to include all delivery statuses for notifications

User Story - Business Need

Our swagger documentations has a single enum, "created", in the schema for the GET v2/notifications response.

There are other delivery statuses than "created", we should complete the enum with all available status strings.

Swagger also provides a Description section for the route, which should be populated with a list or table or paragraph explaining which states are final and which states are transient and will be retried.

This ticket is based off a client request received for more information.

[ ] Ticket is understood, and QA has been contacted (if the ticket has a QA label).

User Story(ies)

As a client of VANotify I want to understand all the possibilities of a notification's delivery status So that I can categorize the states into final/absolute states, and states that are intermediary/transient

Additional Info and Resources

Statuses that should be in the enum:

created
sending
sent
delivered
permanent-failure
technical-failure
temporary-failure
preferences-declined

OpenAPI spec Swagger Editor Our application's swagger document

Acceptance Criteria

[ ] The enum for status in the sms schema for the GET v2/notifications/:notification_id 200 response includes all possible status strings
[ ] The enum for status in the email schema for the GET v2/notifications/:notification_id 200 response includes all possible status strings
[ ] The description for the path includes a section describing which of these statuses are final and which are retried and who retries them (client? VANotify?)
[ ] Portal is notified so that they can pull in these changes to the documentation displayed in the Portal.
[ ] This work is added to the sprint review slide deck (key win bullet point and demo slide)

QA Considerations

[ ] Double-check the work

department-of-veterans-affairs / notification-api